Fast-path canonical PostgreSQL dates

[StevenMcClankerton]

Linked issue

n/a — performance work without a tracking issue

Prerequisite: #30186.

Summary

Fast-paths the canonical PostgreSQL YYYY-MM-DD wire form with direct Temporal.PlainDate construction while retaining the existing parser for every noncanonical representation. On top of the runtime optimization PR, aggregate whole-result-set latency improves from 809.2 µs to 679.0 µs.

At a glance

return new Temporal.PlainDate(
  year0 * 1000 + year1 * 100 + year2 * 10 + year3,
  month0 * 10 + month1,
  day0 * 10 + day1,
);

Only fixed-width ASCII dates reach this constructor path.

Decision

Recognize and validate the ordinary server representation using character codes, then construct the immutable Temporal value directly. BC dates, expanded years, sentinels, malformed input, and other noncanonical forms continue through the existing adaptation and Temporal.PlainDate.from behavior.

Reviewer notes

• Every digit is range-checked before direct construction; length and separator positions are fixed.
• The generic fallback remains the source of behavior and errors outside the canonical form.
• The touched helper also replaces Reflect.get with typed Symbol.toStringTag access while preserving the existing runtime guard, satisfying the production-code structural lint without changing wrong-type handling.

Behavior changes & evidence

• Canonical PostgreSQL dates decode through a fixed-width parser in packages/3-targets/3-targets/postgres/src/core/temporal-codec-helpers.ts.
• Ordinary, BC, expanded-year, sentinel, malformed, non-ISO-calendar, and wrong-type behavior remains covered by packages/3-targets/3-targets/postgres/test/temporal-codecs.test.ts.

Testing performed

• pnpm --filter @internal/target-postgres test — 93 files, 1596 tests
• pnpm --filter @internal/target-postgres typecheck
• Rebuilt framework components, SQL relational core, PostgreSQL target, and SQL runtime before pnpm --filter benchmarks bench
• Aggregate whole-result-set result: 809.2 µs → 679.0 µs (-16.1%); autoresearch best was 652.5 µs (-47.2% from baseline)

Skill update

n/a — internal codec implementation optimization with unchanged public behavior

Checklist

• All commits are signed off (git commit -s) per the DCO.
• I read CONTRIBUTING.md and the change is scoped to one logical concern.
• Tests are updated.
• The PR title is in TML-NNNN: <sentence-case title> form — no Linear ticket exists for this work.
• The Skill update section above is filled in.

Notes for the reviewer

This is the final PR in the stack and contains only the PostgreSQL date-codec optimization plus the typed property-access cleanup required in the touched helper.

Alternatives considered

• Continue using Temporal.PlainDate.from for canonical dates: simpler, but it dominates date-heavy result-set latency.
• Regular-expression validation: rejected after a 4.6% aggregate regression versus character-code validation.
• Bitwise digit-range aggregation: rejected because two-run performance was identical to straightforward scalar checks and readability was worse.
• Cache decoded dates: rejected because changing object identity and retaining an unbounded value set would alter runtime characteristics.

Summary by CodeRabbit

• Performance
  • Improved PostgreSQL date decoding for standard yyyy-mm-dd values.
  • Added validation for date components while enabling faster direct parsing.
  • Retained fallback handling for other supported date formats.
  • Date values now decode more efficiently without changing the supported behavior or output format.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between d20d3ba and 43b39a0.

📒 Files selected for processing (1)

• packages/3-targets/3-targets/postgres/src/core/temporal-codec-helpers.ts

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---

📝 Walkthrough

Walkthrough

The PostgreSQL temporal codec now reads Symbol.toStringTag directly and fast-paths standard yyyy-mm-dd values before using Temporal.PlainDate.from.

Changes

PostgreSQL temporal codec

Layer / File(s)	Summary
Temporal value encoding and date decoding packages/3-targets/3-targets/postgres/src/core/temporal-codec-helpers.ts	The encoder input type accepts an optional Symbol.toStringTag property and reads it through direct property access. Date decoding validates standard date strings and constructs Temporal.PlainDate directly, with Temporal.PlainDate.from as the fallback.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 43b39

This localized PostgreSQL date-decoding optimization preserves fallback behavior for noncanonical inputs, and no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise, specific, and accurately describes the main change: adding a fast path for canonical PostgreSQL dates.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch optimize-decode-postgres-date

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commit: 0380a6c

[github-actions]

size-limit report 📦

Path	Size
postgres / no-emit	175.52 KB (+0.11% 🔺)
postgres / emit	152.67 KB (+0.1% 🔺)
mongo / no-emit	101.09 KB (0%)
mongo / emit	90.95 KB (0%)
cf-worker / no-emit	199.43 KB (+0.08% 🔺)
cf-worker / emit	173.96 KB (+0.11% 🔺)